1. Field of the Invention
The present invention relates to a write device, an image forming apparatus, and an open/close control method.
2. Description of the Related Art
A printer that has an electrophotographic system includes a charge unit, a photoreceptor, a write device, a developing unit, a transfer unit, a fixing unit, a feed unit, and a discharge unit. In the printer, first, the charge unit charges the surface of the photoreceptor. Then, in the printer, the write device irradiates the surface of the photoreceptor with light so as to form an electrostatic latent image, the developing unit develops the latent image to form a developed image, the feed unit feeds a sheet, and the transfer unit transfers the developed image onto the sheet. Finally, in the printer, the fixing unit fixes the developed image to the sheet with applied heat and pressure, and then the discharge unit discharges the sheet to which the developed image is fixed.
The write device has a configuration such that it includes a window to allow the passage of laser light so as to irradiate the photoreceptor with the laser light through the window.
Because the window is a simple opening, the write device includes a dust preventing member to prevent foreign substances, such as paper dust or toner supplied from the developing unit at the developing stage after exposure, from getting inside the write device. The dust preventing member is a transparent optical element, inorganic glass, or the like, which allows the passage of laser light as well as prevents foreign substances from getting inside the write device.
There is a possibility that a user, or the like, spills toner and contaminates the dust preventing member during maintenance, such as when supplying toner or replacing consumables. The dust preventing member can be contaminated during normal use when a print process is being performed. Such contamination of the dust preventing member prevents appropriate exposure of the photoreceptor and, as a result, the desired image formation cannot be performed. Therefore, the user needs to clean the dust preventing member as appropriate.
For example, Japanese Patent Application Laid-open No. H02-244171 discloses an electrophotographic device in which a dust preventing member is mounted on a window, a shutter unit is arranged outside the window to open the window during normal use and close the window during maintenance, and a cleaning unit is attached to the shutter unit to clean the outer surface of the dust preventing member in accordance with the movement of the shutter unit.
In the electrophotographic device, during normal use, the shutter unit is open so that laser light is emitted through the window to irradiate the surface of the photoreceptor with the laser light. Meanwhile, during maintenance, the shutter unit is closed so as to cover the dust preventing member and close the window to cut off the laser light.
In a conventional write device, when the shutter unit is open during normal use or the shutter unit is closed during maintenance, the position of the shutter unit is determined by using one control plate 10 and a plurality of shutter sensors 20 and 21, as illustrated in FIG. 1.
Specifically, if a shutter unit 30 is in the open state, the control plate 10, which is arranged in series with the shutter unit 30, is detected by the shutter sensor 20. If the shutter unit 30 is moved in the direction indicated by the arrow Z and set in the closed state, the control plate 10 is detected by the shutter sensor 21. Thus, the position of the shutter unit 30 can be determined by using the shutter sensors 20 and 21.
However, if a plurality of shutter sensors is used in the write device, the structure is complicated and the manufacturing costs of the write device and the image forming apparatus on which the write device is mounted are increased; therefore, there is a problem in that the write device and the image forming apparatus on which the write device is mounted cannot be provided at a low cost.
Thus, there is a need for a write device and an image forming apparatus that can be provided at a low cost by decreasing the number of sensors so as to simplify the structure and reduce the cost.